Department of Pathology and Cell Biology, Columbia University, New York, NY 10032, USA.
Mol Biol Cell. 2012 Oct;23(20):4032-40. doi: 10.1091/mbc.E12-05-0338. Epub 2012 Aug 23.
In migrating fibroblasts, RhoA and its effector mDia1 regulate the selective stabilization of microtubules (MTs) polarized in the direction of migration. The conserved formin homology 2 domain of mDia1 is involved both in actin polymerization and MT stabilization, and the relationship between these two activities is unknown. We found that latrunculin A (LatA) and jasplakinolide, actin drugs that release mDia1 from actin filament barbed ends, stimulated stable MT formation in serum-starved fibroblasts and caused a redistribution of mDia1 onto MTs. Knockdown of mDia1 by small interfering RNA (siRNA) prevented stable MT induction by LatA, whereas blocking upstream Rho or integrin signaling had no effect. In search of physiological regulators of mDia1, we found that actin-capping protein induced stable MTs in an mDia1-dependent manner and inhibited the translocation of mDia on the ends of growing actin filaments. Knockdown of capping protein by siRNA reduced stable MT levels in proliferating cells and in starved cells stimulated with lysophosphatidic acid. These results show that actin-capping protein is a novel regulator of MT stability that functions by antagonizing mDia1 activity toward actin filaments and suggest a novel form of actin-MT cross-talk in which a single factor acts sequentially on actin and MTs.
在迁移的成纤维细胞中，RhoA 和其效应因子 mDia1 调节向迁移方向极化的微管 (MTs) 的选择性稳定。mDia1 的保守的formin 同源 2 结构域既参与肌动蛋白聚合又参与 MT 稳定，而这两种活性之间的关系尚不清楚。我们发现，Latrunculin A (LatA) 和 Jasplakinolide，肌动蛋白药物，可将 mDia1 从肌动蛋白丝的帽状末端释放，刺激血清饥饿的成纤维细胞中稳定的 MT 形成，并导致 mDia1 在 MT 上重新分布。小干扰 RNA (siRNA) 敲低 mDia1 可阻止 LatA 诱导的稳定 MT 诱导，而阻断上游 Rho 或整合素信号无影响。在寻找 mDia1 的生理调节剂时，我们发现肌动蛋白加帽蛋白以 mDia1 依赖的方式诱导稳定的 MT，并抑制 mDia 在生长肌动蛋白纤维末端的易位。siRNA 敲低加帽蛋白可降低增殖细胞和用溶血磷脂酸刺激的饥饿细胞中的稳定 MT 水平。这些结果表明，肌动蛋白加帽蛋白是 MT 稳定性的一种新型调节剂，通过拮抗 mDia1 对肌动蛋白纤维的活性起作用，并提示一种新的肌动蛋白-MT 串扰形式，其中单个因子依次作用于肌动蛋白和 MT。
